Satin-finished nickel or nickel alloy coating

ABSTRACT

In order to achieve an even satin-finished nickel or nickel alloy coating an acid nickel or nickel alloy electroplating bath is proposed which contains a sulfosuccinic acid compound of the general formula I additional to at least one quaternary ammonium compound, wherein R 1 , R 2 =hydrogen ion, alkali ion, alkaline earth ion, ammonium ion and/or C 1 -C 18  hydrocarbon moiety, wherein R 1  and R 2  are identical or different with the proviso that at the most one of the groups R 1  and R 2 =hydrogen ion, alkali ion and alkaline earth ion, and wherein K + =hydrogen ion, alkaline ion, alkaline earth ion, ammonium ion.

FIELD OF THE INVENTION

[0001] The invention relates to an acid nickel or nickel alloyelectroplating bath and to a method for depositing a satin-finishednickel or nickel alloy coating.

BACKGROUND OF THE INVENTION

[0002] Predominantly bright nickel or nickel alloy coatings whichmoreover should be well levelled are used in industry. However, it hasbeen recognized early that satin-finished coatings may look estheticallyand at the same time prevent from dazzling. When combined withsemi-bright nickel coatings and with a chromium coating such coatingsare just as corrosion preventing as a bright nickel coating. Thesesatin-finished nickel coatings are therefore often used in automotiveindustry, in precision mechanics industry, for sanitary appliances aswell as for furniture mountings.

[0003] Up to now nickel coatings can be produced with various methods:

[0004] It has been indicated in DE-OS 1 621 085 that the surface of themetal to be coated could first be roughened by means of sandblasting.Afterwards the surface would then be treated with a commonelectroplating bath to deposit a bright nickel layer. According toanother method first a bright nickel coating could be provided with amat finish by means of mechanical treatment. Due to this treatment,however, the corrosion resistance would be reduced considerably becausethe nickel layer would be weakened. It is further indcated that bothmethods described would suffer from being very complicated and expensivedue to the mechanical treatment. Other methods are described in thisdocument which allow deposition of satin-finished nickel coatingsdirectly from the electroplating bath without any preceding orsucceeding mechanical treatment. For this purpose finely grindedmaterial which is unsoluble in these baths, such as for example kaolin,graphite, barium sulfate, glass, talcum powder, calcium oxalate andother substances, with a particle size of from 0.1 to 0.3 μm are addedto the common nickel electroplating baths in considerable amounts. Byintensively blowing air through the baths these substances are held insuspension and will be codeposited into the coating as nickel isdeposited. It is indicated in this document that a certain roughness ofthe coating would emerge establishing satin-finished appearance. Thismethod, however, would require a specific apparatus for carrying out themethod, since the method could not be performed in conventionalelectroplating devices. For this reason additional costs would arise.

[0005] Because of the drawbacks of the conventional methods an acidnickel electroplating bath for the production of satin-finished nickelcoatings is disclosed in DE-OS 1 621 985 as an improvement over thedescribed methods in this document. For performing this method a bath isrequired that, additional to basic brightening compounds, containssubstituted or unsubstituted ethylene oxide or propylene oxide orethylen oxide propylene oxide adducts at a concentration of from 5 to100 mg/l, these additional adducts being able to form a finely dispersedemulsion in the bath solution at a temperature of from 40 to 75° C.

[0006] Further an acid nickel, nickel/cobalt or nickel/ironelectroplating bath are described in DE 25 22 130 B1, these baths beingsuitable for the deposition of satin-finished coatings. This bathcontains liquid polysiloxane polyoxyalkylene block polymers in anemulsion in addition to primary and/or secondary brighteners.

[0007] Nickel coatings that are known from the disclosure in DE-OS 1 621085 can be produced according to the method as described in DE-AS 1 621087. Coatings exhibiting even satin-finish can be produced by coolingthe bath liquid completely or partly below cloud temperature andsubsequent heating the liquid to the working temperature again. Uponexeeding the cloud temperature nonionic surfactants precipitate due tothe fact that the surfactants loose their hydrate sheath. The emulsifieddroplets formed are dissolved upon cooling the liquid and will once morebe formed upon anewed heating. The nickel deposition is impairedselectively by precipitating droplets of the surfactant, without thedroplets essentially being included into the nickel coating. The factthat much energy must be spent for heating and cooling the platingliquid as well as for pumping the liquid makes this methoddisadvantageous. Furthermore the maximum bath volume is limited to acertain value since the expenditure for heating and cooling the liquidand for pumping the liquid raises considerably if the bath volumeexceeds 8.000 l. Under these conditions operation of the method is nolonger economical. Moreover after a short time of carrying out thismethod lumps of the surfactants are formed in the bath solution whichcause pores to be produced in the nickel coatings.

[0008] Due to the drawbacks mentioned above the method for producingsemi-bright nickel or nickel/cobalt coatings as described in DE 23 27881 A1 has been successful. In this method the mat coatings aregenerated by incorporating foreign matter into the coatings. The foreignmatter is produced by bringing together cationic or amphotericsubstances with organic anions. Quaternary ammonium compounds,derivatives of imidazolines, alcanolamine esters and surface activeagents based on amino carboxylic acids are proposed in this document ascationic or amphoteric substances. By bringing together the cationic oramphoteric substances with the organic anions an emulsion is formedwhich together with basic brighteners being present in the nickelelectroplating bath leading to a satin-finish by imparing nickeldeposition.

[0009] Unfortunately this method also suffers from certain drawbacks:Within about three to five hours after making up the electroplating baththe surface of deposited nickel coatings becomes more and more rough. Inpart even visually detectable coarse nickel crystals appear on thesurface which are not acceptable as to the appearance of the nickelsurface. Therefore at least before eight hours of production have passedthe bath liquid must be worked up by completely filtrating and cleaningit with filter material, such as for example cellulose, diatomaceousearth or even with activated carbon. The production break required forworking the bath liquid up is especially very troublesome and expensiveif a continuous plant is operated. Moreover a removable “silver layer”is generated if afterwards a chromium layer is deposited for 10 minutesor longer.

[0010] Several attempts have been made to get rid of the shortcomingsmentioned. Therefore in DE 37 36 171 A1 a method for the deposition ofsatin-finished nickel coatings is described, the nickel bath liquid usedfor carrying out this method containing inter alia one or more basicbrighteners, one or more anionic surfactants, one or more organicemulsion formers, one or more quaternary ammonium compounds as well asone or more acyclic or aromatic sulfinic acids. Preferably benzoic acidsulfimide, m-benzenedisulfonic acid, naphthalenetrisulfonic acid,diaryidisulfides, sulfonamides and N-sulfonyl carboxamides as well asthe salts thereof being soluble in water are to be understood as basicbrighteners. However, upon carrying out this method coatings with aconstant appearance cannot be achieved without heating and cooling thebath liquid as before.

[0011] A further electroplating method for producing nickel coatingsthat have a non-dazzling appearance is disclosed in DE 195 40 011 A1.According this document a nickel bath is used, that contains inter aliabasic brighteners, organic sulfinic acids as well as surfactants.Additionally the bath contains substituted and/or unsubstituted ethyleneoxide adducts or propylene oxide adducts or ethylene oxide propyleneoxide adducts at such a low concentration that cloudiness is notvisually detectable at the working temperature of the bath. The use ofnonionic surfactants at the concentration indicated in this documentdoes not guarantee, however, since their efficiency quickly diminishesand since the appearance of the coatings quickly changes.

[0012] Further an aqueous electroplating bath for depositing brightnickel or nickel/cobalt coatings is described in DE 21 34 457 C2.According to several examples in this document sulfosuccinic acid estersare added to the bath liquid which additionally contains saccharin as asecondary brightener. However, satin-finished nickel coatings were notproduced with these baths.

[0013] Furthermore a nickel bath for depositing satin-finished coatingsis disclosed in Patent Abstracts of Japan, JP 56152988 A which containssurfactants selected from the group comprising alkyl aryl sulfonates andsulfosuccinic acid esters additional to saccharin as a brightener andethylene oxide propylene oxide block polymer. In this case too it has beestablished that a satin-finished nickel coating could only be producedwithin a short period after the bath has been made up. After this periodcoatings were generated which exhibit a rough surface.

[0014] All methods described can only be carried out during a few hours.Within this period nickel coatings with more or less satisfactorysatin-finish are obtainable. However, during this period of timeroughness increases. After expiry of this period only rough nickelcoatings can be deposited which are porous.

[0015] The problem of the present invention therefore consists inavoiding the disadvantages of the known electroplating baths andespecially in finding an electroplating bath suitable for the productionof a satin-finished nickel or nickel alloy coating and a method forproducing satin-finished nickel coatings. When using this method itshould be possible to generate nickel coatings with constant surfacequality within a long period of time after the electroplating bath hasbeen made up without the necessity to clean the bath liquid or work thebath up with any other means with excessive expenditure.

SUMMARY OF THE INVENTION

[0016] Surprisingly it has been found out that satin-finished coatingscan be obtained on the surface of nickel and nickel alloy layers beingdeposited at any point of time within a long period of time after makeup of the bath, if one or more sulfosuccinic acid compounds are added toa nickel electroplating bath, which additionally contains at least onequaternary ammonium compound and at least one anionic basic brightener,the sulfosuccinic acid compound having the following general formula(I):

[0017] wherein

[0018] R₁, R₂=hydrogen ion, alkali ion, alkaline earth ion, ammonium ionand/or C₁-C₁₈ hydrocarbon moiety, wherein R₁ and R₂ are identical ordifferent with the proviso that at the most one of the groups R₁ andR₂=hydrogen ion, alkali ion, ammonium ion and alkaline earth ion, and

[0019] wherein

[0020] K⁺=hydrogen ion, alkaline ion, alkaline earth ion, ammonium ion.

[0021] The constancy of nickel electroplating is likely to be the resultof the stability of the ion pair crystals being formed from thequaternary ammonium compounds and the anionic basic brighteners, whichconstancy may even be enhanced by at least twice by employing thesulfosuccinic acid compounds. The efficiency of the sulfosuccinic acidcompounds in accordance with the inventive purpose obviously resultsfrom the effect of these compounds act as a co-dispersant for the ionpair crystals as mentioned. This also results from the fact that even alow concentration of the sulfosuccinic acid compounds in theelctroplating bath is sufficient to assure the effect according to theinvention. By adding the sulfosuccinic acid compounds to theelectroplating bath it is possible for the first time to operate thebath for days with a partial current filtration.

[0022] The present invention is not related to mat nickel electroplatingbaths.

[0023] There are a variety of advantages of the nickel or nickel alloyelectroplating baths according to the present invention:

[0024] 1. The stability of the dispersion formed in the electroplatingbath is improved by at least twice the continuous operating timecompared to conventional baths.

[0025] 2. An operation for days is possible by means of partial currentfiltration.

[0026] 3. Formation of a removable “silver layer” upon chromium platingis prevented.

[0027] 4. The satin-finished appearance is enhanced by addition of thesulfosuccinic acid compounds. This is appreciated by those applicantswho want to deposit nickel or nickel alloy coatings with a substantialsatin-finish. Up to now such an appearance was only achieved by addingquaternary ammonium compounds in considerable amounts to the nickelelectroplating bath. However under these conditions bath life wasreduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] At least one of the C₁-C₁₈ hydrocarbon moieties of thesulfosuccinic acid compound I is preferably an acyclic or cyclichydrocarbon moiety or a group of hydrocarbon moieties bridged via ethergroups. The C₁-C₁₈ moieties are preferably acyclic linear or unbranchedmoieties or cyclic moieties. If necessary these moieties may also beunsaturated hydrocarbon moieties or groups of at least partlyunsaturated hydrocarbon moieties bridged via ether groups.

[0029] The compounds listed in table 1 have proven a success when theyare employed in an nickel or nickel alloy electroplating bath. TABLE 1Sulfosuccinic acid compounds 1 sulfosuccinic acid di(n-propyl) ester 2sulfosuccinic acid di(iso-propyl) ester 3 sulfosuccinic acid di(n-butyl)ester 4 sulfosuccinic acid di(iso-butyl) ester 5 sulfosuccinic aciddi(n-pentyl) ester 6 sulfosuccinic acid di(iso-pentyl) ester 7sulfosuccinic acid di(n-hexyl) ester 8 sulfosuccinic acid di(iso-hexyl)ester 9 sulfosuccinic acid bis-(1,3-dimethylbutyl) ester 10sulfosuccinic acid dicyclohexyl ester 11 sulfosuccinic acid di(n-octyl)ester 12 sulfosuccinic acid di(iso-octyl) ester 13 sulfosuccinic acidbis(2-ethylhexyl) ester 14 sulfosuccinic acid dinonyl ester 15sulfosuccinic acid monolauryl ester 16 sulfosuccinic acid dilauryl ester17 sulfosuccinic acid monododecenyl ester 18 sulfosuccinic aciddihexadecyl ester 19 fatty alcohol polyglycol ether ester ofsulfosuccinic acid 20 sulfosuccinic acid mono(oxodiethoxydodecyl) ester(lauryl alcohol polyglycol ether ester of sulfosuccinic acid)

[0030] The alkyl ester group may especially comprise all isomers. Forexample the propyl ester comprises n-propyl ester and iso-propyl ester,the butyl ester comprises n-butyl ester, iso-butyl ester and tert.-butylester and the pentyl ester comprises the n-pentyl ester, the iso-pentylester, the tert.-pentyl ester and the neo-pentyl ester.

[0031] Both free sulfonic acid and the sodium, potassium and magnesiumor ammonium salts thereof may be employed. Usually the sodium salts ofthe sulfonic acid are used. Furthermore also several sulfosuccinic acidcompounds may be used.

[0032] The concentration of the sulfosuccinic acid compounds in thenickel or nickel alloy electroplating baths is very low and may bevaried in the range from 0.005 to 5 g/l and normally of from 0.005 to0.05 g/l. The concentration of the sulfosuccinic acid compounds ispreferably near the upper limit of the preferred concentration range (upto 0.05 g/l) if the effect to be achieved should last as long aspossible. It has to be considered that commercially available substancesare rarely pure to 100 %, but normally contain water and sometimes alsolower alcohols as solubilizers. The aforementioned concentrations referto substances with a purity of 100 %.

[0033] The bath liquid provided for the electroplating of nickel ornickel alloy deposits usually comprises a nickel salt solution whichadditionally contains a weak acid as a buffer substance in addition tothe substances in accordance to the present invention.

[0034] In general practice a so-called Watts electrolyte is used, whichhas about the following composition:

[0035] 330-550 g/l nickel sulfate (NiSO₄.7 H₂O)

[0036] 30-150 g/l nickel chloride (NiCl₂.6 H₂O)

[0037] 30-50 g/l boric acid (H₃BO₃)

[0038] The pH of the electrolyte solution may be set in the range from 3to 5.5, mainly from 3.8 to 4.4. In order to be able to set a currentdensity as high as possible the temperature may amount up to 75° C. Ingeneral it is set in the range from 50° C. to 60° C.

[0039] Nickel and nickel alloy electroplating baths have a chloridecontent of from 10 to 50 g/l. The best results are obtained with bathswith a concentration in this range. Nickel chloride may be replacedpartly or entirely by sodium chloride. Chloride in the electrolyte maybe replaced partly or entirely by equivalent amounts of bromide. Nickelsalts in the electroplating bath can be replaced at least partly bycobalt salts or at least one cobalt ion source may be added to the bathin order to be able to deposit a nickel/cobalt alloy coating. Thecathodic current density may amount to values up to 10 A/dm² if thetemperature amounts to 55° C. and if a high-performance electroplatingbath as mentioned is employed. Usually the current density is set to 3to 6 A/dm². The dwell time in the nickel electroplating bath shouldamount to at least 9 minutes under the conditions given.

[0040] In principle sulfosuccinic acid compounds may be added to thebath without any other bath additives to be added too. However,sufficient long-time stability of the baths can only be achieved if acombination of the sulfosuccinic acid compounds is used together withquaternary ammonium compounds and if necessary with additional basicbrighteners. Under these circumstances an excellent satin-finish ofnickel or nickel alloy surfaces is achieved over the entire currentdensity range operable under practical conditions. This excellentsatin-finish may be achieved constantly at least during 15 hours ofoperation of the electroplating bath. Furthermore plating under thementioned conditions does not lead to removable haze on a chromiumplated layer on top of the nickel or nickel alloy coating even if a longchromium plating time is set.

[0041] The quaternary ammonium compounds contained in the nickel ornickel alloy bath are cationic surface active agents having thefollowing general formula (II):

[0042] wherein

[0043] R₁, R₂ and R₃=hydrogen and/or acyclic C₁-C₁₈ hydrocarbon moiety,wherein R₁, R₂ and R₃ are identical or different with the proviso thatat most two of the moieties R₁, R₂ and R₃=hydrogen;

[0044] R₄=hydrogen, acyclic C₁-C₄ hydrocarbon moiety or C₁-C₄hydrocarbon moiety substituted with an aromatic group, for examplebenzyl;

[0045] X^(p−)=monovalent or multivalent anion, for example chloride,bromide, formiate or sulfate; and

[0046] p=an integer.

[0047] R₁, R₂ and R₃ are linear or branched saturated and if necessaryunsaturated C₁-C₁₈ hydrocarbon moieties. Mixtures of hydrocarbonmoieties of naturally occuring acids, such as for example the tallo,cocosyl, myristyl and lauryl moiety, may advantageously be employed.

[0048] Examples of the quaternary compounds are given in table 2: TABLE2 Quaternary ammonium compounds 1 dioctyldimethyl ammonium chloride 2didecyldimethyl ammonium chloride 3 didodecyldimethyl ammonium bromide 4dodecyl dimethylbenzyl ammonium chloride 5 tetradecyldimethylbenzylammonium chloride 6 hexadecyldimethylbenzyl ammonium chloride 7cocosyldimethylbenzyl ammonium chloride 8 stearyldimethylbenzyl ammoniumchloride 9 oleyldimethylbenzyl ammonium chloride 10 dilauryldimethylammonium bromide

[0049] The concentration of the quaternary ammonium compounds is set toa value in the range from 0.1 to 100 mg/l, preferably from 2.5 to 15mg/l. Surfactants commonly used for preventing the deposition of porouscoatings are not added to the nickel or nickel alloy electroplatingbath. Most of these compounds impair the nickel or nickel alloydeposition. The goods to be plated are slowly moved in the plating bath.An additional aeration of the plating solution is seldomly employed.Circulating pumps and if necessary an overflow are frequently required.These improve the evenness of the satin-finished nickel or nickel alloylayer.

[0050] Further basic brighteners may preferably be added to the nickelor nickel alloy electroplating bath. Unsaturated, in most cases aromaticsulfonic acids, sulfonamides, sulfimides, N-sulfonylcarboxamides,sulfinates, diarylsulfones or the salts hereof are to be understood asbasic brighteners. The most familiar compounds are for examplem-benzenedisulfonic acid, benzoic acid sulfimide (saccharin),trisodium-1,3,6-naphthalenetrisulfonate, sodium benzene monosulfonate,dibenzene sulfonamide and sodium benzene monosulfinate.

[0051] Known basic brighteners are given in table 3. Mostly the sodiumor potassium salts thereof are used. Furthermore it is also possible toemploy several basic brightners at the same time. TABLE 3 Basicbrighteners 1 m-benzenedisulfonic acid 2 vinylsulfonic acid 3allylsulfonic acid 4 propinsulfonic acid 5 p-toluenesulfonic acid 6p-toluenesulfonamide 7 benzoic acid sulfimide 81,3,6-naphthalenetrisulfonic acid 9 N-benzoylbenzenesulfonamide

[0052] The basic brighteners given in table 3 are employed and added tothe electrolyte bath at a concentration of from 5 mg/l to 10 g/l,preferably of from 0.5 to 2 g/l. If merely the basic brighteners areadded to the Watts basic preparation a bright deposit is obtained withina limited current density range. Therefore mere application of the basicbrightener without addition of any other additive has no practicalimportance. Only by further addition of quaternary ammonium compoundsthe satin-finish as wanted is achieved.

[0053] Satin-finished nickel or nickel alloy layers are produced on anelectrically conductive work piece, for example on an work piececonsisting of a metal, with a method, comprising the following methodsteps:

[0054] a. bringing the work piece into contact with a nickel or nickelalloy electroplating bath according to the present invention;

[0055] b. bringing at least one anode into contact with the nickel ornickel alloy electroplating bath;

[0056] c. applying a voltage across the work piece and the at least oneanode; and

[0057] d. electrodepositing a satin-finished nickel or nickel alloycoating on the work piece.

[0058] In order to achieve a satin-finished surface as stable aspossible it is necessary to circulate and/or filtrate the bath solutioncontinuously or intermittently. This means that part of the bathsolution is either continuously or from time to time passed out of theelectroplating container and recirculated back to the bath containeragain. If necessary the bath solution is filtrated when it has left thebath container. Due to this operation bigger lumps of ion paircrystallites, these crystallites in general being necessary to producethe satin-finished surface, are removed from the bath solution in orderto maintain the mean particle size of these crystallites continuouslyunder a certain critical value.

[0059] In the following examples are given to more clearly describe thepresent invention:

Example 1.0

[0060] To an electrolyte solution having the following composition:

[0061] 370 g/l nickel sulfate (NiSO₄.7 H₂O)

[0062] 40 g/l nickel chloride (NiCl₂.6 H₂O)

[0063] 40 g/l boric acid (H₃BO₃)

[0064] 3 g/l sodium salt of benzoic acid sulfimide (basic brightener;compound I)

[0065] are first added 0.006 g/l didodecyidimethyl ammonium bromide(quaternary ammonium compound II).

[0066] The electrolyte solution was examined in a 100 l sized containerbeing equipped with a mechanism for translational motion of the goodsand maintaining the bath solution at a temperature of 55° C. For thispurpose a scratched and 7 cm×20 cm sized copper sheet was electroplatedfor 17 minutes at a cathodic current density of 2.5 A/dm². An evensatin-finished nickel coating was produced on the whole surface area ofthe copper sheet. Neither pits nor black pores were visible. Thisprocedure was repeated each hour, the electroplated sheets beingcompared to each other. Already after a time period of 4 hours a coarsesurface appearance of the nickel coatings was detected. After a 5 hoursperiod the experiment was stopped since the coatings meanwhile hadbecome unsightly (uneven, mat).

EXAMPLE 1.1

[0067] First 0.02 g/l sulfosuccinic acid bis-(1,3-dimethylbutyl)-ester(compound I) und further 0.006 g/l didodecyidimethyl ammonium bromide(compound II) were added to the electrolyte solution of example 1.0.

[0068] The examination of the electroplating bath was carried out asdescribed in example 1.0. An even satin-finished appearance was detectedon the whole surface area of the sheet electroplated with nickel.Neither pits nor black pores were visible. Electroplating was repeatedeach hour under the conditions as indicated above, the electroplatedsheets being compared to each other. Already after a time period of 4hours a coarse surface appearance of the nickel coatings was detected.After a 15 hours period the experiment was stopped since no change forthe worse could be detected as to the appearance of surface quality ofthe nickel coatings produced.

[0069] Results of examples 1.0 and 1.1: Without employing compound I(sufosuccinic acid bis-(1,3-dimethylbutyl) ester) only a life time ofthe bath solution of 4 to 5 hours was achieved. Upon addition ofcompound I a life time of more than 15 hours was achieved.

EXAMPLE 2.0

[0070] To an electrolyte solution having the following composition:

[0071] 450 g/l nickel sulfate (NiSO₄.7 H₂O)

[0072] 80 g/l nickel chloride (NiCl₂.6 H₂O)

[0073] 40 g/l boric acid (H₃BO₃)

[0074] 3 g/l sodium salt of allylsulfonic acid (basic brightener)

[0075] 5 g/l sodium salt of benzoic acid sulfimide (basic brightener)

[0076] were first added 0.01 g/l cocosyldimethylbenzyl ammonium chloride(quaternary ammonium compound II).

[0077] The electrolyte solution was examined in a 100 l sized containerbeing equipped with a mechanism for translational motion of the goodsand maintaining the bath solution at a temperature of 55° C. startingonly after an idle time of 30 minutes. For this purpose a scratched andangled, 7 cm×20 cm sized copper sheet was electroplated for 20 minutesat a cathodic current density of 3 A/dm². Thereafter the sheet waschromium plated for 12 minutes in a commercial chromium bath (BrightChrome CR 843, Atotech Deutschland GmbH, DE) at 40° C. at a currentdensity of 10 A/dm².

[0078] An even satin-finished nickel coating was obtained on the wholesurface area of the copper sheet. Upon looking at the surface of thenickel plated sheet towards a light source a haze could be detected(so-called “silver layer”). After operation of the nickel electroplatingbath for 5 hours this faint removable haze had evolved to an easilyvisible haze so that production had to cease.

EXAMPLE 2.1

[0079] First 0.04 g/l sulfosuccinic acid dihexyl ester (compound I) wereadded to the electrolyte solution used in example 2.0. Then 0.01 g/lcocosyldimethylbenzyl ammonium chloride (quaternary ammonium compoundII) was added to the solution.

[0080] The examination of this bath solution was performed as describedin example 2.0. After an idle time of 30 minutes an even satin-finishednickel coating was obatined on the whole surface area of the sheet.Neither pits nor black pores were visible. Upon looking at the surfaceof the nickel plated sheet towards a light source no haze could bedetected. Even after operation of the nickel electroplating bath for 5hours no haze could be detected.

[0081] Result of examples 2.0 and 2.1: Addition of compound I accordingto the present invention (sufosuccinic acid dihexyl ester) preventedoccurence of a haze on the nickel surface even after an operation timeof the bath of 5 hours.

EXAMPLE 3.0

[0082] To an Erlenmeyer flask were given the following substancessucceedingly whereas the mixture was stirred:

[0083] 50 ml water

[0084] 1.5 g/l sodium salt von allylsulfonic acid (basic brightener)

[0085] 5 g/l sodium salt of benzoic acid sulfimide (basic brightener)

[0086] 20 mg/l didecyldimethylbenzyl ammonium chloride (quaternaryammonium compound II).

[0087] The surface of the solution was examined by means of a slit lamp.After about 1 hour had passed a clear scale-like, iridescent surfacefilm appeared. The solution was turbid.

EXAMPLE 3.1

[0088] Parallel to example 3.0 the following substances were given tothe Erlenmeyer flask:

[0089] 50 mg water

[0090] 1.5 g/l sodium salt of allylsulfonic acid (basic brightener)

[0091] 5 g/l sodium salt of benzoic acid sulfimide (basic brightener)

[0092] 10 mg/l sulfosuccinic acid diisooctylester (compound I).

[0093] Then upon stirring 20 mg/l dodecyidimethylbenzyl ammoniumchloride (quaternary ammonium compound II) were added to this solution.Even after 16 hours no surface film had been developped. The solutionwas slightly turbid.

[0094] Result of examples 3.0 and 3.1: Without employing compound I aclear scale-like iridescent surface film developped on the electrolytesolution. Upon addition of compound I even after a 16 hours period nosurface film developped!

EXAMPLE 4.0

[0095] To 400 ml of an electrolyte solution having the followingcomposition:

[0096] 350 g/l nickel sulfate (NiSO₄.7 H₂O)

[0097] 40 g/l nickel chloride (NiCl₂.6 H₂O)

[0098] 40 g/l boric acid (H₃BO₃)

[0099] 1 g/l sodium salt of 1,3,6-naphthalenesulfonic acid (basicbrightener)

[0100] 3 g/l sodium salt of benzoic acid sulfimide (basic brightener)

[0101] 100 mg/l cocosyldimethylbenzyl ammonium chloride (quaternaryammonium compound II) were added. During the time period of 16 hours thesample was held at a temperature of 55° C. Through floating a filmdevelopped on the surface of the solution. This film could easily bedetected by means of a slit lamp.

EXAMPLE 4.1

[0102] First 3.5 mg/l sulfosuccinic acid dihexyl ester (compound Iaccording to the present invention) were added to the electrolytesolution of example 4.0. After stirring the solution again 100 mg/lcocosyldimethylbenzyl ammonium chloride (quaternary ammonium compoundII) were added. The samples were held at a temperature of 55° C. for 16hours. Through floating a very thin film developped on the surface ofthe electrolyte solution. This film could just be detected by means of aslit lamp.

EXAMPLE 4.2

[0103] First 10 mg/l sulfosuccinic acid dihexyl ester (compound I) wereadded to the electrolyte solution of example 4.0. After stirring thesolution again 100 mg/l cocosyidimethylbenzyl ammonium chloride(quaternary ammonium compound II) were added. The samples were held at atemperature of 55° C. for 16 hours. By means of a slit lamp practicallyno film could be detected on the electrolyte surface.

[0104] Result of examples 4.0 4.1 and 4.2: Addition of the compound Ieven at a concentration of 10 mg/l prevented generation of a film whichwould impair electroplating. Even at a concentration of 3.5 g/l apositive effect could be detected.

1. Acid nickel or nickel alloy electroplating bath for depositing a satin-finished nickel or nickel alloy coating containing a sulfosuccinic acid compound having the general formula (I)

wherein R₁, R₂=hydrogen ion, alkali ion, alkaline earth ion, ammonium ion and/or C₁-C₁₈ hydrocarbon moiety, wherein R₁ and R₂ are identical or different with the proviso that at the most one of the groups R₁ and R₂=hydrogen ion, alkali ion, ammonium ion and alkaline earth ion, and wherein K⁺=hydrogen ion, alkaline ion, alkaline earth ion, ammonium ion and at least one quaternary ammonium compound, having the following formula (II)

wherein R₁, R₂ and R₃=hydrogen and/or acyclic C₁-C₁₈ hydrocarbon moiety, wherein R₁, R₂ and R₃ are identical or different with the proviso that at most two of the moieties R₁, R₂ and R₃=hydrogen; R₄=hydrogen, acyclic C₁-C₄ hydrocarbon moiety or C₁-C₄ hydrocarbon moiety substituted with an aromatic group; X^(p−)=monovalent or multivalent anion; and p=an integer.
 2. Acid nickel or nickel alloy electroplating bath according to claim 1, wherein at least one of the C₁-C₁₈ groups of the sulfosuccinic acid compound are acyclic or cyclic hydrocarbon moieties or groups of hydrocarbon moieties bridged via ether groups.
 3. Acid nickel or nickel alloy electroplating bath according to any of the preceding claims, wherein the at least one sulfosuccinic acid compound is contained in the bath at a concentration of from 0.005 to 5 g/l.
 4. Acid nickel or nickel alloy electroplating bath according to any of the preceding claims, wherein the at least one sulfosuccinic acid compound is contained in the bath at a concentration of from 0.005 to 0.05 g/l.
 5. Acid nickel or nickel alloy electroplating bath according to any of the preceding claims, wherein at least one sulfosuccinic acid compound is contained in the bath, selected from the group comprising sulfosuccinic acid dipropyl ester, sulfosuccinic acid dibutyl ester, sulfosuccinic acid dipentyl ester, sulfosuccinic acid dihexyl ester, sulfosuccinic acid dicyclohexyl ester, sulfosuccinic acid dioctyl ester, sulfosuccinic acid dinonyl ester, sulfosuccinic acid monolauryl ester, sulfosuccinic acid dilauryl ester, sulfosuccinic acid monododecenyl ester, sulfosuccinic acid dihexadecyl ester, fatty alcohol polyglycol ether ester of sulfosuccinic acid and sulfosuccinic acid mono(oxodiethoxydodecyl) ester.
 6. Acid nickel or nickel alloy electroplating bath according to any of the preceding claims, wherein the at least one sulfosuccinic acid compound is one of the salts thereof selected from the group comprising the potassium salt, the sodium salt, the ammonium salt and the magnesium salt.
 7. Acid nickel or nickel alloy electroplating bath according to any of the preceding claims, wherein the at least one quaternary ammonium compound is contained in the bath at a concentration of from 0.1 to 100 mg/l.
 8. Acid nickel or nickel alloy electroplating bath according to any of the preceding claims, wherein additionally at least one basic brightener is contained in the bath at a concentration of from 0.005 to 10 g/l.
 9. Acid nickel or nickel alloy electroplating bath according to any of the preceding claims, wherein additionally at least one cobalt ion source is contained in the bath
 10. Method for depositing a satin-finished nickel or nickel alloy coating on an electrically conductive work piece, comprising the following method steps: a. bringing the work piece into contact with a nickel or nickel alloy electroplating bath according to any of claims 1 to 9; b. bringing at least one anode into contact with the nickel or nickel alloy electroplating bath; c. applying a voltage across the work piece and the at least one anode; and d. electrodepositing a nickel or nickel alloy coating on the work piece.
 11. Method according to claim 10 wherein the nickel or nickel alloy electroplating bath is filtered or circulated continuously or intermittently. 